What Is Potassium Silicate?
Potassium Silicate is a silicate of potassium with the chemical formula K2SiO3.
It is either a white solid at room temperature or a highly viscous, fizzy liquid, similar to water glass.
It is synthesized by the reaction of potassium silicate with potassium hydroxide in a wet or dry process.
It often exists in a hydrated water state and is known to have various compositions such as K2O, SiO2, and H2O, but most of these are obtained at temperatures above 200°C and their presence has not been confirmed at room temperature.
Uses of Potassium Silicate
Potassium Silicate is used for a variety of purposes, but is most often used as a fertilizer for plants. Potassium, along with calcium and magnesium, is necessary for plant growth, so these minerals are blended with compounds of silicate and sold as potassium silicate fertilizers.
Many are industrially manufactured with a SiO2 to K2O ratio (molar ratio) of 2~3, and are used as a coating material for welding rods, a hardener for paints, and a raw material for detergents, among others, with compositions to suit their applications.
Properties of Potassium Silicate
Potassium Silicate is often handled in aqueous solution. It is similar to sodium silicate in characteristics, being a viscous liquid, colorless, odorless, and strongly alkaline. Contact with skin and eyes causes irritation. It mixes freely with water and is insoluble in ethanol. It is stable under normal conditions, but reacts with acids to form silica gel.
Hydrous crystals of sodium silicate are well known, such as sodium metasilicate 9-hydrochloride, sodium metasilicate 5-hydrochloride, and sodium sesquisilicate 5-hydrochloride.
In contrast, the conditions for the presence of hydrous crystals of potassium silicate are very limited.
Structure of Potassium Silicate
Silicate tetrahedra are bonded via shared oxygen atoms to form a three-dimensional network of silicon and oxygen atoms. Potassium silicate cations are incorporated into the network, filling the spaces between the silicate tetrahedra and balancing the negative charge of the oxygen atoms.
In aqueous solution, they exist as chained metasilicate ions rather than orthosilicate ions. As the concentration of potassium silicate ions decreases, the silicate ions become branched and cross-linked, resulting in a network structure.
Other Information about Potassium Silicate
1. Use of Potassium Silicate as a Fertilizer
Potassium Silicate is often used as a fertilizer because it provides plants with both potassium and silicon, nutrients essential for plant growth and development. It is produced as a fertilizer by mixing it with fly ash or magnesium hydroxide and calcining it.
Potassium is one of the essential nutrients for plants and is required for a variety of physiological processes, including photosynthesis, water regulation, and protein synthesis.
Although silicon is not considered an essential nutrient for plants, it has been shown to have many beneficial effects on plant growth and health, including increased resistance to pests and diseases and tolerance to non-living stresses such as drought and heat.
2. Environmental Safety of Potassium Silicate Fertilizers
Potassium Silicate fertilizers are considered environmentally safe. They have a pH of about 10, but because they are a physiologically neutral fertilizer, changes in soil pH are small. In addition, they do not run off with rainwater, etc., allowing nutrients to be retained in the soil and slowly released to plants.
3. Use of Potassium Silicate as a Surface Modifier
When potassium silicate is used as a concrete surface modifier, even if cracks occur after construction, water causes the modifier to react with the calcium hydroxide inside the concrete to form a gel with a composition similar to cement hydrate.
It forms a waterproof and deterioration-preventive protective layer and can repair cracks on its own. The waterproofing and deterioration-preventing effect can be demonstrated over a long period of time, resulting in highly durable concrete structures and reduced life-cycle costs.
It is often used mixed with sodium silicate.